JP2002347180A - Coextrusion film or the like, and tape products and manufactured goods or the like including them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coextrusion film having elongation properties at breaking point of a vertical direction which does not exceed about 35% that is similar to such elongation properties at breaking point of a vertical direction realized by a traditional non-coextrusion film or the like in markets, and to provide a coextrusion adhesive tape incorporating an adhesive agent repulsive peeling coating or the like that does not need an adhesive agent repulsive peeling layer at all or that can be applied at lower cost and in a more efficient manner. SOLUTION: In a film including a base layer (A) and a reinforced layer adhered to (B) and (A), (B) comprises a material stronger than that of (A), (B) forms a continuous layer on a surface of (A), and thickness of (B) is smaller by 25% than a total thickness of (A)+(B).

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to a method for producing a co-extruded film, a film produced thereby, tape products including the film, and uses of the tape products.

[0002] 2. 2. Description of the Related Art Uniaxially oriented polypropylene ("MOPP") films are well known. These films are typically made into bulk precursor films by processing polypropylene granules through a film die and then forming the precursor films into, for example, a roll-type stretch frame ( On a roll-type drawing frame), it is manufactured by a process of producing a final MOPP film by stretching in one direction.

[0003] The stretching operation is "arranging" MOPP films.
As a result, they are generally characterized by a high tensile strength in the direction of stretching. At the same time, these MOPP films are characterized by an unacceptable weakness in the transverse direction perpendicular to the stretching direction.

[0004] When the films are cut into tapes or other products, "micronicks" may appear along either longitudinal edge.
Because the film is weak in the transverse direction, these micro-cuts tend to expand in the transverse direction, ultimately leading to breakage.

In US Pat. No. 5,093,187 to Engelmann et al., The entire disclosure of which is incorporated herein by reference, for example, co-extruding a polypropylene film with a layer of polyethylene film co-extrudes this problem. Has been resolved. This second layer is more tough than the polypropylene film in that it is resistant to the formation of fine cuts. Since the second layer is adhered to the polypropylene layer, no fine cuts are formed in the polypropylene layer, or even if the fine cuts are formed, they do not develop in the lateral direction. Extruded tapes are more difficult to break.

[0006] Engelman et al.
Teaches that the base layer or layers occupy 65 to 75% of the thickness of the coextruded film, which indicates that the second layer, e.g.
It means that the coextruded polyethylene layer should make up the remaining 25-35%. See column 5, lines 16-21. Thus, for example, the most preferred films are those of the examples, but these have a total thickness of 83-87 μm.
m, of which the thickness of 60 to 63 μm is the polypropylene base layer, which is the remaining 20 to 2 μm.
A thickness of 7 μm means the second layer. Especially the sixth
See column lines 29-33.

Applicants have characterized that films made at these ratios have unacceptably high elongation at break in the longitudinal direction, which makes them unsuitable for some purposes. I discovered what I was doing. For example, these tapes are used to tear open closed structures such as envelopes and boxes. These tapes are applied to closed structures on the production line. At the desired high line speeds, these films are pulled longitudinally, stretched over a portion of a closed structure, and then glued to the structure and cut. Since the elongation at break in the longitudinal direction is unacceptably large,
These tapes exhibit rubber band-like properties, rebound when cut, and provide inadequate coverage for closed structures.

In practice, the elongation at break in the longitudinal direction should not exceed 35%, which is what Engelman et al. Showed by non-coextruded comparative tapes A, B and C. . Table 1 from column 8, line 41
checking ... As a control, tapes such as Engelman et al. Are reported to be characterized by an elongation at break in the longitudinal direction of at least 40%, although commercial embodiments within the patent range include elongation at break in the longitudinal direction. Is at least 55%
Applicants have discovered that

Another problem associated with MOPP films, especially adhesive tapes made therefrom, is that when unwound from a roll, such tapes are "shreated."
It has the characteristics of “dding” or “fibrillation.” When wound up in a roll, the adhesive layer is bonded to the polypropylene layer, which causes the tape to be unwound from the roll. The adhesive peels off the filaments of the polypropylene layer, resulting in a shattered appearance of the tape, which not only greatly impairs the aesthetic appearance of the tape, but also due to the presence of these debris sticking to the adhesive In addition, a large number of such fragments will lead to a large decrease in tack.

[0010] Engelmann et al. Solved this problem by coating an adhesive-repellant release layer on one side of the uncoated adhesive film. See col. 5, lines 66-68. However, the examples use a commercially available silicone release lacquer. See column 6, lines 39-42. The use of silicone release lacquers increases production costs and drying times and reduces production rates.

SUMMARY OF THE INVENTION Accordingly, one object of the present invention is to provide a longitudinal elongation at break similar to that exhibited by conventional non-coextruded films on the market, ie, not exceeding about 35%. The purpose of the present invention is to provide a coextruded film having an elongation at break.

Another object of the present invention is to provide coextrusion adhesives that do not require any adhesive repellent release layer or incorporate adhesive repellent release coatings that would otherwise be cheaper and more efficient to apply. Is to provide tape.

[0013] These and other objects are achieved by the present invention, a first embodiment of which comprises (A) a base layer, and
(B) a film including a reinforcing layer adhered to (A), wherein (B) is made of a tougher material than (A);
(B) forms a continuous layer on the surface of (A), and
The thickness of (B) relates to a film that is less than 25% of the total thickness of (A) + (B).

The reason why the reinforcing layer (B) is described as being made of a material which is more tough than the "base layer (A)" is that the reinforcing layer (B) is subjected to an impact load which has already caused brittle fracture of the base layer (A). Means that the reinforcing layer (B) is deformed without breaking. Accordingly, the reinforcing layer (B) preferably has higher impact strength, elongation and energy absorption.

Compared to the films disclosed by Engelman et al., The films of the present invention are characterized by outstanding film properties. As can be seen from the foregoing, the films disclosed by Engelman et al. Are reported to be characterized by an elongation at break in the machine direction of at least 40%, and commercial embodiments falling within the scope of this patent are at least The films of the present invention are characterized by about 35% elongation at break in the longitudinal direction of 55%.
The elongation at break in the longitudinal direction that does not exceed.

Surprisingly, the improved properties of the films of the present invention are achieved without loss of tensile strength. Thus, for example, 63 μm thick films made in accordance with the present invention have a thickness of 70-80 N / 4 mm, measured in the longitudinal direction.
The ultimate tensile stress of On the other hand, the thickness is 83 ~
Exemplified films, such as Engelman, changed to 85 μm showed ultimate tensile stress of 65-73 N / 4 mm.
The higher tensile stress of the films of the present invention is surprising since the tensile strength increases almost linearly with increasing thickness. Therefore, it is expected that the thinner the inventive film, the lower the tensile strength, but this was not observed.

DETAILED DESCRIPTION OF THE INVENTION Generally, the selection of materials for the base layer and the reinforcing layer is as described in Engelmann et al. The main difference between the films of the present invention and Engelman's films lies in the thickness of the reinforcing layer and the properties derived therefrom. The films of the present invention are:
It may consist of multiple base layers and reinforcement layers, in which case the total thickness of all base layers and reinforcement layers should not exceed the parameters described here.

Accordingly, the base layer is composed of a polypropylene-olefin copolymer and / or a polypropylene-toughening additive mixture. In a preferred embodiment, the base layer comprises mainly impact-modified polypropylene, preferably at least 70%. For this purpose, preference is given to using random or block copolymers of propylene and olefins.

The base layer may contain up to 100% of propylene-olefin copolymers and may contain up to 25% of reinforcing additives in admixture with these copolymers. This is suitable for improving the transverse impact tensile strength of polypropylene. Preferred toughening additives are linear low density polyethylene (LLDP)
E), thermoplastic rubbers such as butadiene-styrene copolymers (SBS) and isoprene-styrene copolymers (SIS), in particular, in each case, block copolymers thereof, or ethylene-vinyl acetate ( EVA).

The base layer may comprise a polypropylene homopolymer, in which case the reinforcing additives are also preferably present in at least 10% but not more than 30%.

Mixtures of propylene-olefin copolymers and propylene homopolymer can also be used. In this embodiment, the proportion of reinforcing additives may be reduced as the proportion of copolymer increases.

Preferably, the toughening agents are added individually. However, mixtures of reinforcing agents can also be used.

The base layer contains 75 to 100% of a copolymer and L
LDPE is 25 to 0%, or copolymer is 80 to 10%.
0% and a thermoplastic rubber, especially SBS or SIS of 20 to
Preferably, it contains 0% or 75 to 100% of a copolymer and 25 to 0% of EVA. Particularly preferred is 80
-95% copolymer and 5-20% LLDPE, or 85-95% copolymer and 5-15% thermoplastic rubber, especially SBS or SIS, or 85-95% copolymer And a blend of 5-15% EVA.

In a particularly preferred embodiment, the base layer comprises a propylene-ethylene copolymer, which is blended with a linear low density polyethylene as a reinforcing agent to provide a copolymer to blended polyethylene ratio of from 75:25 to 75:25. 9
5: 5, preferably in the range of 90:10 to 95: 5.

For the reinforcing layer disposed on the base layer, it is preferred that it comprises a distinctly higher proportion of reinforcing additives, is characterized by a higher impact tensile strength than the base layer, or both materials. Are used. The reinforcing layer comprises polypropylene, as specified for the base layer, in particular up to 65% of propylene-olefin copolymer or up to 55% of propylene homopolymer, preferably in each case preferably at least 20% , To which 35 or 45 to 80% of reinforcing additives, in particular LLDPE, thermoplastic rubbers or EVA are added. Preferably, the reinforcing additives are added individually. However, again, mixtures of reinforcing additives can be used. Again, mixtures of polypropylene-olefin copolymers and propylene homopolymers can be used. As in the base layer, the toughening additive provides an improvement in impact tensile strength, especially in its transverse direction.

The reinforcing layer contains 20 to 50% of the copolymer and L
LDPE 80 to 50%, or copolymer 50 to 7
0% and thermoplastic rubber, especially SBS or SIS 50 to 50%
Preferably, it contains 30% or 20-40% copolymer and 80-60% EVA, but the reinforcing layer is 30-40% copolymer and 60-70% LLDPE or copolymer. 55-65% coalescing and thermoplastic rubber, especially S
35 to 45% of BS or SIS, or 2% of copolymer
It is particularly preferred to contain 5 to 35% and 65 to 75% EVA.

In a particularly preferred embodiment, the reinforcing layer comprises a propylene-ethylene copolymer, which is blended with a linear low density polyethylene to provide a copolymer to blended polyethylene ratio of from 50:50 to 25:25. 75,
Preferably, it is in the range of 40:60 to 30:70.

For good compatibility between the layers, the same toughening is used for the base layer and the reinforcing layer.
agent). However, it is also possible to use different fortifiers or to use different mixtures of fortifiers.

LLDPE specifically intended for it is
Having a density of about 0.910, copolymerized with an olefin containing at least 3, preferably 3 to 10 carbon atoms.
It is a special ethylene copolymer of 0.935 g / cm ³ . L. Schwiegk: "LLDP
E-ein neues Polyathylen (LLDPE-new polyethylene) ", Plastverarbeiter (secondary processor of plastics), 33rd year, 1982, N
o. See pages 9,1035-1037.

For preferred substrate films according to the present invention, LLDs having 1-octene as comonomer
PE having a density of about 0.920 g / cm ³ is used.

It is preferred to use a block copolymer having a styrene content of around 50% as a butadiene-styrene reinforcing agent. It is likewise possible to use styrene-isoprene copolymers which act in a similar manner.

Preferably, a polymer having a vinyl content of about 45% is used as the EVA copolymer.

The base layers and / or reinforcing layers may furthermore contain further suitable polymers and / or customary additives in a smaller proportion, preferably up to 10%, in particular up to 5%.

The films of the present invention are preferably obtained by co-extruding the material of the individual layers into a coextruded primary film, and then stretching the primary film in at least one direction using conventional techniques. It is also possible to extrude and stretch the individual layers and then laminate the individual layers together. Stretching is preferably performed in the machine direction.

The stretch ratio in the machine direction, as defined by column 5, lines 3 to 13 of Engelmann, is preferably from 1: 5 to 1: 9, in particular from 1: 6.5 to 1: 7. 5

The final film thickness is such that the total thickness of all the reinforcing layers is less than 25%, preferably less than 15%, particularly preferably less than 10% of the total film thickness. . Referring now to FIG. 1, a film 10 according to the present invention comprising a base layer 11 and a reinforcing layer 12 is shown.
Is shown. In a preferred embodiment,
The thickness of the base layer 11 is in a range from about 60 μm to about 125 μm, and the thickness of the reinforcing layer 12 is in a range from about 2 μm to about 10 μm. If there is more than one base layer and / or more than one reinforcement layer, the total thickness of the base layers is in the range of about 60 μm to about 125 μm, and the total thickness of the reinforcement layers is in the range of about 2 μm to about 10 μm. In a particularly preferred embodiment, a thickness of about 6
There is a single base layer ranging from 0 μm to about 125 μm and a single reinforcing layer ranging from about 3 μm to about 5 μm in thickness.

Referring now to FIG. 2, the films of the present invention can be incorporated into a tape product 20, which exhibits the advantageous properties described above. The tape product depicted in this figure comprises a base layer 11, a reinforcing layer 12, an adhesive layer 21, a primer layer 22, and an optional adhesive repellent release coating layer 23. Adhesive layer, primer layer,
And for the optional release coating layer,
Any conventional materials may be used. This adhesive is
It is preferable to select from the group consisting of a natural rubber-based adhesive, a synthetic rubber-based adhesive and an acrylic adhesive, and a hot-melt adhesive, a solvent-based adhesive or a water-based adhesive. In one preferred embodiment, a release coating layer is present, such as, for example, ESCOAT P-2 from Anderson Development.
0 (trademark) or Mazo Corporation
n) consists of a carbamate-based release coating such as a polyvinyl octadecyl release coating such as RA95-H ™. In another preferred embodiment, the tape product has no release coating.

The tapes of the present invention are applied to articles of manufacture for various well-known purposes, such as, for example, for tearing and reinforcing. In the preferred embodiment depicted in FIG. 3, the article of manufacture is a strip 31 of the tape product of the present invention.
Series of packaging bags 3 in which individual bags 32 are connected to each other by
0. In another preferred embodiment depicted in FIG. 4, the article of manufacture is an envelope 40 containing a tear tab 41 for opening it after sealing.
The tear knob 41 is reinforced by a tape product 42 according to the present invention. Tear tapes similar to these
apes) are well known and are used to open many types of packages, such as detergent boxes, cigarette packages, as well as envelopes. In another preferred embodiment depicted in FIG. 5, the article of manufacture is a shopping bag 50 having an opening 51 in a handle region, the openings being a vertical tape product strip 52 and a horizontal tape product strip. 53 reinforces all sides. This type of reinforcement is useful, for example, in all types of articles, such as edges in photo albums, holes in notebook paper, as well as shopping bags.

When cutting the coextruded film into tapes, use a regular blade (regu
Preferably, a lar blade is used. A regular blade has a normal edg with substantially no fine cuts.
e) forming. Notwithstanding the above, if it is desired to form a fine notch so that the tapes can be intentionally easily torn in the lateral direction, the film may be cut using, for example, a serrated blade. It can be cut into tapes.

The invention will now be described in more detail with reference to the following non-limiting examples. Examples Impact modified polypropylene (Shell 7C06 ™ resin), linear low density polyethylene [Dow 20
32 (trademark) resin] and a colorant [10
51672 Red ™] from the blend
A 0 mm wide base layer was extruded from the main extruder. The ratio of impact modified polypropylene to linear low density polyethylene is
It was 93 to 7 by weight%. The main extruder consisted of five zones, which ran at temperatures between 215 and 250 ° C.

On this base layer, 7C06 ™ resin, 2C
032 ™ resin and defibrillating agent (defibrilla)
A 1530 mm wide reinforcement layer was co-extruded from a co-extruder from a blend of ting agent (also a HY6100 ™ resin from Shell). 7C06 ™: 2
The 032 ™: HY6100 ™ ratio was 39.6: 60.3: 0.1 by weight. This co-extruder consists of three zones, which are also 215 and 250
Operated at a temperature between ° C.

After extrusion, the film was first heated to 35 to 40 ° C.
And then passed through two chill rolls and one glazing roll operating at 80-85 ° C. Thereafter, the film was passed through a preheating roll operating at around 108 ° C and then stretched at 120 ° C. Following this, the film was annealed by passing it over an annealing roll operating at 130 ° C. and then passing over a series of gradually cold chill rolls.

By changing the amount of the extruded material, three kinds of tapes of the present invention having respective thicknesses of 63, 72 and 120 μm were produced. For comparison, 63 μm and 120 μm films without any reinforcement layer (“no PE”) were also extruded. 63 μm PE-free film is
80% by weight of HY6100 ™ and 2032 ™
Of 20% by weight. 120 μm PE
The neat film consisted of 7C06 ™ and a small amount of colorant. The resulting films exhibited the properties shown in Table 1.

[0044]

[Table 1] ¹ PE indicates the presence of a polyethylene layer of the indicated thickness.

The specification and claims are provided by way of explanation, not limitation, and it is recognized that various modifications and changes may be made without departing from the spirit and scope of the invention. Will.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a two-layer film according to the present invention.

FIG. 2 is a schematic diagram of a five-layer tape product according to the present invention.

FIG. 3 is a schematic view of a series of three packaging bags connected to each other by two strips of tape product according to the present invention.

FIG. 4 is a schematic view of an envelope that has been sealed and then modified to be opened by pulling on a tape reinforced with a tape product according to the present invention.

FIG. 5 is a schematic view of a shopping bag reinforced around a handle opening with a strip of tape product according to the present invention.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Trumper, Richard, Allan, Jr. United States 49330 Wengal Road, Kent City, Michigan 12969 F-term (reference) 4F100 AK03A AK03B AK04A AK04B AK07A AK07B AK25G AL01A AL01B AL05A AL05B AN01G AN02G AT00A BA03 BA07 BA10A BA10B BA10C BA25 CB01G CB03G CB10H EH20 EH202 GB15 JK02B JL14C YY00A YY00B 4J004 AA04 AA05 AA10 AB03 CC03 4J040 CA011 CA031 DF001 JA03 JA09 JB01

Claims (21)

[Claims] 1. A film comprising: (A) a base layer; and (B) a reinforcing layer adhered to (A), wherein (B) is made of a material that is stronger than (A),
(B) forms a continuous layer on the surface of (A), and
A film in which the thickness of (B) is less than 25% of the total thickness of (A) + (B). 2. The film according to claim 1, wherein the base layer (A) comprises a polypropylene-olefin copolymer. 3. The film according to claim 2, wherein the base layer (A) further comprises a blended polyethylene. 4. The film according to claim 3, wherein the ratio of the blended polyethylene to the polypropylene-olefin copolymer in the base layer (A) is in the range from 25:75 to 5:95. 5. The film according to claim 1, wherein the reinforcing layer (B) comprises polyethylene. 6. The film according to claim 5, wherein the reinforcing layer (B) further comprises a blended polypropylene-olefin copolymer. 7. The film according to claim 6, wherein the ratio of blended polypropylene-olefin copolymer to polyethylene in the reinforcing layer (B) is in the range from 50:50 to 25:75. 8. The base layer (A) has a thickness of about 60 μm to about 1 μm.
25 μm, and the thickness of the reinforcing layer (B) is about 2 μm.
A film according to any one of claims 1 to 7, ranging from m to about 10 [mu] m. 9. The reinforcing layer (B) has a thickness of about 3 μm to about 5 μm.
9. A film according to claim 8 in the range of μm. 10. The film according to claim 8, which is produced by co-extruding said base layer (A) with said reinforcing layer (B). 11. A tape product comprising (A) a film according to any one of claims 1 to 10, and (B) an adhesive coated on the film (A). 12. The tape product according to claim 11, wherein said adhesive is selected from the group consisting of a natural rubber adhesive, a synthetic rubber adhesive, and an acrylic adhesive. 13. The adhesive according to claim 13, wherein the adhesive is a hot melt adhesive.
13. The tape product according to claim 12, which is a solvent-based adhesive or a water-based adhesive. 14. The tape product according to claim 11, further comprising an adhesive-repellent release material coated on the film (A) opposite to the side coated with the adhesive (B). 15. The tape product according to claim 14, wherein the adhesive-repellent release material is a carbamate-based release coating. 16. The tape product according to claim 15, wherein the adhesive is selected from the group consisting of a natural rubber adhesive, a synthetic rubber adhesive, and an acrylic adhesive. 17. The adhesive according to claim 17, wherein the adhesive is a hot melt adhesive.
17. The tape product according to claim 16, which is a solvent-based adhesive or a water-based adhesive. 18. Article of manufacture comprising a tape product according to any one of claims 11 to 17. 19. The article of manufacture according to claim 18, comprising a series of packaging bags glued in series by said tape product. 20. An article of manufacture according to claim 18 including the tape product and including a sealed package adapted to be opened by pulling one end of the tape product. 21. The article of manufacture according to claim 18, comprising a container reinforced with said tape product.